The present invention relates to an anticorrosive treatment method for a separator of a molten carbonate fuel cell, and more particularly, to an anticorrosive treatment method for a separator of a molten carbonate fuel cell which improves an anticorrosive capability with respect to an electrolyte and prevents deformation of the molten fuel cell at the time of heat treatment, by coating nickel and aluminium in turn or only aluminium on a base material of a stainless steel, or by bonding an aluminium thin film thereon and then performing a diffusion processing thereto.
Generally, a molten carbonate fuel cell generates an electrical energy in used as an oxidizing agent, both mutually react, and hydrogen contained in the fuel and oxygen contained in the oxidizing agent mutually electrochemically react. The molten carbonate fuel cell is regarded as a fourth electric power following hydraulic, thermal, and atomic electric power. Such a fuel cell directly converts chemical energy of the reacting materials into electrical energy, to guarantee high efficiency as well as low pollution.
A general structure of the fuel cell will be described below. FIG. 1 shows a general molten carbonate fuel cell, which purposes for explaining an inner layer structure and driving mechanism of the molten carbonate fuel cell. As shown in FIG. 1, the fuel cell includes electrodes 10a and 10b composed of a anode electrode and an cathode electrode between which an electrochemical reaction is performed, matrixes 20a and 20b interposed between the electrodes in order to contain and support an molten carbonate of a electrolyte, current collectors 30a and 30b for smoothing the movement of electrons generated from the reaction, and separators 40a and 40b for providing entry and exit of reaction gases and an electric current path. The electrodes 10a and 10b use nickel-chromium (Ni--Cr) as an anode electrode and nickel oxide (NiO) as a cathode electrode. A mixed carbonate consisting of 62% by mole of Li.sub.2 CO.sub.3 and 38% by mole of K.sub.2 CO.sub.3 is used as the electrolyte. Lithiumaluminate (LiAlO.sub.2) is used as the matrixes 20a and 20b. It is appropriate to use stainless steel such as AISI 316L and AISI 310S as the material of the separators 40a and 40b.
However, in the case of the above molten carbonate fuel cell, nickel oxide of the cathode electrode is dissolved and corroded by reaction with the electrolyte in the cathode electrode contacting thereto, to bitterly cause loss of the electrolyte. Particularly, the molten carbonate fuel cell operates at a high temperature of 650.degree. C., to accordingly corrode a wet-seal area contacting the electrolyte on the separator severely. Such a corrosion causes the electrolyte to be consumed. As a result, cross-over of the reaction gases and the short-circuit of the cell due to the corrosion products results in deterioration of the performance of the cell and shortening of the lifetime thereof.
Accordingly, to solve the above problems, aluminium coating has been performed on the wet-seal area of the fuel cell, which is regarded as the best anticorrosive coating method. As general aluminium coating methods, there are a molten aluminium coating method in which a base material is dipped into the molten aluminium, and a calorizing method in which Al, NH.sub.4 Cl, and Al.sub.2 O.sub.3 are mixed and thermally treated to then diffuse Al into the base material. Besides, there are a physical vapor deposition method for evaporating aluminium and depositing it on the base material, a slurry coating method for coating slurry obtained by mixing aluminium powder with various solvents on the base material, a spray coating method for spraying aluminium onto the base material.
The above-described general aluminium coating methods perform a diffusion thermal treatment at 900.degree. C. or more. In this case, since the separator is thin, the high temperature heat generated during operation of the fuel cell deforms the plates. Also, defects due to high temperature thermal treatment cause to corrode even the base materials of stainless steel, to be shortened the lifetime of the fuel cell thereby. Further, unless the aluminium is coated by a predetermined thickness or more (minimum 30 .mu.m), an anticorrosive capability cannot be enough for. To prevent this, a coating ratio should be heightened finally, which makes fabrication of the large-area separator difficult, and manufacturing costs high.